When you engage in the Top Down troubleshooting approach, you are using the OSI reference model as a guide, and you are hoping that the problem is one of the higher layers! You are beginning your troubleshooting in the higher layers, trying to find the highest layer that is working. You see, the way the OSI reference model works, if we can determine that a particular layer works, then it is a pretty safe assumption that all the layers below it are functional. Notice I say “pretty” safe. There might indeed be problems at a lower layer that are so specific, they are not showing up in your initial evidence collection.  [Read More]